DCT

1:22-cv-01160

TurboCode LLC v. D Link Corp

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:22-cv-01160, W.D. Tex., 04/26/2023
  • Venue Allegations: Venue is alleged to be proper because the defendant is a foreign corporation, making venue appropriate in any U.S. judicial district.
  • Core Dispute: Plaintiff alleges that Defendant’s 3G/4G/LTE-capable routers and adapters infringe a patent related to high-speed, power-efficient decoder architectures for error correction in wireless communications.
  • Technical Context: The technology concerns "turbo codes," a type of forward error correction used in 3G and 4G cellular standards to ensure the integrity of data transmitted over noisy wireless channels.
  • Key Procedural History: The complaint notes that the patent-in-suit has been successfully enforced against other parties and that this enforcement is ongoing. Plaintiff provided formal notice of infringement to the Defendant on October 18, 2021. The asserted patent, U.S. Patent No. 6,813,742, was the subject of an ex parte reexamination, which resulted in the cancellation of two claims and the amendment of the asserted claims.

Case Timeline

Date Event
1999-05-26 '742 Patent Priority Date
2004-11-02 '742 Patent Issue Date
2016-01-01 Alleged Infringement Start Date (approximate)
2021-10-18 Plaintiff Provided Notice of Infringement to Defendant
2023-04-26 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 6,813,742 - "High speed turbo codes decoder for 3G using pipelined SISO log-map decoders architecture"

The Invention Explained

  • Problem Addressed: The patent addresses the challenge of implementing powerful "turbo code" decoders in early 3G mobile devices. Existing decoding methods, such as the Maximum a Posteriori (MAP) algorithm, were highly effective but computationally intensive, requiring complex multiplier circuits that were slow, costly, and consumed too much power for practical use in battery-operated devices ('742 Patent, col. 2:44-60).
  • The Patented Solution: The invention proposes a decoder architecture that uses two serially connected "Soft-In/Soft-Out" (SISO) decoders operating in a pipelined, iterative loop ('742 Patent, Fig. 4). The architecture performs calculations in the logarithmic domain (Log-MAP), which replaces complex multiplications with simpler, faster binary adder circuits ('742 Patent, col. 3:3-6). This pipelined, iterative process allows the decoder to achieve high data throughput (one decoded output per clock cycle) with lower power consumption and a simpler hardware implementation suitable for mass-market wireless devices ('742 Patent, Abstract; col. 2:31-43).
  • Technical Importance: The described architecture sought to make high-performance error correction feasible for the high-data-rate, low-power, and low-cost requirements of the emerging 3G cellular market ('742 Patent, col. 2:23-28).

Key Claims at a Glance

  • The complaint asserts independent claim 6, as amended by the ex parte reexamination certificate ('742 Re-exam Cert., col. 2:13-52; Compl. ¶38, ¶43).
  • Essential elements of amended claim 6 include:
    • A method for iterative decoding comprising:
    • providing an input buffer with at least three shift registers to generate first, second, and third shifted input signals;
    • providing first and second soft decision decoders "serially coupled in a circular circuit," where the first decoder receives the first/second shifted signals and the second decoder receives the third;
    • providing memory modules coupled to the decoders, where the output of the second decoder's memory is fed back as an input to the first decoder;
    • processing data using a "maximum a posteriori (AP) probability algorithm, and/or logarithm approximation algorithm";
    • generating, weighing, and storing soft decision information;
    • performing iterative decoding for a predetermined number of times in the circular circuit.
  • The complaint notes that dependent claims are also infringed and reserves the right to assert them (Compl. ¶38).

III. The Accused Instrumentality

Product Identification

The "Exemplary Accused Products" are various D-Link 4G LTE routers and adapters, including models DWR-222, DWR-910, DWR-932C, and DWR-921 (Compl. ¶16).

Functionality and Market Context

The accused products are described as telecommunications devices that provide mobile broadband connectivity by operating on 3G and/or 4G/LTE mobile networks (Compl. ¶15, ¶17). The complaint alleges these products are designed to comply with the 3rd Generation Partnership Project (3GPP) technical standards for cellular communication (Compl. ¶11, ¶16). This standards-compliance is presented as evidence of infringement. The complaint includes a technical specifications table for the DWR-932 router, which details its support for UMTS/HSDPA/HSUPA (3G) and FDD-LTE (4G) network technologies (Compl. ¶18, p. 4). A user manual screenshot for the DWR-222 is also provided, showing icons that indicate compatibility with 3G, 4G, and LTE networks (Compl. ¶20, p. 5).

IV. Analysis of Infringement Allegations

The complaint references a claim chart in an external exhibit (Exhibit 3) that was not provided with the filed document (Compl. ¶43). The infringement theory is therefore summarized based on the narrative allegations within the complaint.

The central allegation is that the Accused Products infringe the ’742 Patent because they are built to comply with 3G and/or 4G/LTE cellular standards (Compl. ¶38). The complaint asserts that practicing these standards requires using the patented decoding method recited in claim 6 (Compl. ¶43). This standards-essentiality argument forms the basis of the infringement claim, with the complaint alleging that "Each of the elements of Claim 6 is practiced in the Exemplary Accused Products" by virtue of their 3G/4G/LTE capabilities (Compl. ¶43). The complaint alleges the products process data using a "sliding window" method for improved efficiency, which it connects to the goals of the patented invention (Compl. ¶35).

  • Identified Points of Contention:
    • Technical Questions: A primary question for the court will be whether compliance with the cited 3G/4G/LTE standards mandates the use of a decoder architecture that meets every limitation of the amended claim 6. The dispute may turn on whether the standards allow for alternative, non-infringing decoder implementations.
    • Scope Questions: The case may focus on the degree of architectural correspondence between the accused devices and the claims. For example, does the accused products' hardware and software implement a "circular circuit" with the specific feedback path from the second decoder to the first, as required by the claim? Evidence of the actual implementation within the products' chipsets and firmware will be critical, as high-level marketing materials or standards documents may not resolve this technical question.

V. Key Claim Terms for Construction

  • The Term: "serially coupled in a circular circuit" (from amended Claim 6)

    • Context and Importance: This phrase defines the core architecture of the invention. The infringement analysis will depend heavily on whether the arrangement of decoders in the accused products constitutes a "circular circuit." Practitioners may focus on this term because Defendant could argue its products employ a different architecture (e.g., a parallel, non-iterative, or single-decoder system) that falls outside this definition.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The specification describes two decoders (A and B) connected in a "feedback loop" with memory modules in between, which supports a general topological reading of a circular data path ('742 Patent, col. 4:9-13).
      • Evidence for a Narrower Interpretation: Figure 4 depicts a very specific arrangement where Decoder A feeds an Interleaver Memory, which feeds Decoder B, which in turn feeds a De-Interleaver Memory that provides feedback to Decoder A. A party could argue the term is limited to this specific two-decoder, two-memory feedback structure ('742 Patent, Fig. 4; col. 8:60-col. 9:11).

  • The Term: "logarithm approximation algorithm" (from amended Claim 6)

    • Context and Importance: The patent's claimed advantage is simplifying complex MAP calculations by operating in the log domain. The scope of this term is crucial for determining infringement. If the accused devices use an exact MAP calculation or a different type of approximation, infringement may be avoided.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The claim uses the phrase "and/or," positioning this term as an alternative to a full "maximum a posteriori (MAP) probability algorithm" ('742 Re-exam Cert., col. 2:19-22). The specification's summary states a goal of performing the "entire MAP algorithm in Log domain," which could support a broad definition covering any simplification achieved by log-domain processing ('742 Patent, col. 3:3-6).
      • Evidence for a Narrower Interpretation: The detailed description discloses a specific implementation using "Add-Compare-Select (ACS) logic" to find maximum values ('742 Patent, col. 5:55-58). A party may argue that the term should be narrowly construed to mean the specific max-log-MAP type of approximation detailed in the patent, not any and all possible logarithmic approximations.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement. Inducement is based on Defendant allegedly instructing and encouraging customers to use the products in an infringing manner via "instructions and specifications" (Compl. ¶39). Contributory infringement is based on the allegation that Defendant sells a material component of the invention that is not a staple article of commerce and is especially adapted for infringement (Compl. ¶40).
  • Willful Infringement: Willfulness is alleged based on Defendant’s knowledge of the patent since at least October 18, 2021, the date Plaintiff provided a formal notice of infringement (Compl. ¶36, ¶39). The prayer for relief seeks enhanced damages under 35 U.S.C. § 284 (Compl. p. 10).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of standards-based infringement: Can the Plaintiff demonstrate that compliance with the broad 3G/4G/LTE standards necessarily requires the accused products to practice the specific multi-step method of amended Claim 6, or do the standards permit the use of alternative, non-infringing decoder designs?
  • A key evidentiary question will be one of architectural correspondence: Does the internal circuitry of the accused D-Link products actually implement two decoders arranged in the "serially coupled... circular circuit" with an iterative feedback loop as claimed, or is there a fundamental mismatch in technical operation and architecture?